Cable television is a system for delivering television signals to subscribers or viewers by means of coaxial cable. For an installation charge and a monthly fee, cable television viewers receive a clear picture of local channels, as well as reception of several dozen additional channels including one or two devoted to movies, sports, news or special events. Originating in 1949 as a way of providing good signal reception to geographic areas where the conventional television signals were weak, cable spread quickly among rural municipalities, and can now be found servicing over half the television viewers in the United States.
In 1972, the Federal Communications Commission (FCC) adopted Rules and Regulations requiring cable television operators to obtain a certificate of compliance from the Commission prior to constructing or operating a cable television system. These rules covered a number of broad subjects such as franchising standards, signal carriage, network program duplication and syndication, non broadcast or cablecasting services, and technical standards. Since that time, the Commission has modified or eliminated a number of these Rules and Regulations. Currently, the Commission's Rules and Regulations, as found in 47 Code of Federal Regulations, Section 76, cover such matters as the use of aeronautical frequencies (47 C.F.R .sctn..sctn.76.610, 76.612, 76.618, 76 619), and technical standards (47 C.F.R. .sctn..sctn.74.641, 76.601, 76.605, 76.609-76.619), as well as other matters.
In the 1980's a conflict arose between cable television operators and the aviation industry because the frequencies used by the cable television operators to transmit television signals overlapped those used by the aviation industry. When signals above a certain power level "leak" from a cable plant into the atmosphere, they conflict with those used by the aviation industry for communication, etc. Signal leakage can occur in a variety of situations such as when the shielding of cable cracks or becomes weathered, when connectors become loose or when the cable breaks.
In 1985, the Commission adopted a set of technical standards that require cable television operators to monitor their plants for "leakage" of signals from their cables. Of particular relevance is 47 C.F.R. .sctn.76.614 which requires cable television operators "transmitting carriers in the frequency bands 108-137 and 225-400 MHz [to] provide a program of regular monitoring for signal leakage by substantially covering the plant every three months." Rule 614 continues with the technical specifications regarding the power measurements that must be made, the requirements for logging the power measurements, and the signal strengths that are allowed if a plant is to continue operation.
To fulfill the requirements of Rule 614, and to maintain control over a cable plant, cable television operators have developed a variety of programs to monitor signal leakage. The most common method is to send a team of repairmen into the field with a bucket truck and a spectrum analyzer. Every three months this team drives the truck along every street where cable is installed. One of the repairmen monitors the readings of the spectrum analyzer while the other one drives. When a signal is encountered that is above that allowed under Rule 614, the source of the signal is located, and the cable is repaired.
Another method of monitoring cable plants include the use of an RF meter to measure signal strength while a driver travels along cable paths. The vehicle used by the driver need not be a bucket truck since no repairs are made at this time. When a signal is encountered that exceeds a designated value, the driver logs the value onto a map for later reference. The map is then provided to a repairman who can repair the leak.
While these methods of monitoring a cable plant meet the requirements of Rule 614, they have certain disadvantages. One problem with the first method is that of cost. The first method incurs the operational expense of a bucket truck and the salaries associated with qualified repairmen. The second method takes advantage of the lower operational cost of the vehicle, and the potentially lower salary of the driver. However, the monitoring of the RF meter and the logging of the measurements is still a manual, time consuming process that is subject to human error.
Cable television operators typically transmit the television signals in the frequency bands 108-137 and 225-400 MHz. The allocation of these frequency bands and the restrictions imposed on operators are governed by Title 47 of the United States Code (i.e., The Communications Act of 1934), and by subsequent regulations adopted by the Federal Communications Commission.